PLC Simulator
Runnable instrumentation case

Scale a 4–20 mA Valve Position Feedback Signal

A valve positioner returns a 4–20 mA feedback signal while the PLC command is held at 90%. The measured feedback is 18.4 mA. This page owns that exact calculation job and opens the matching server-graded case rather than a generic calculator.

10 minutes Instrumentation students, calibration technicians and PLC programmers
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Follow the workflow

Learn one step, use the product, inspect the evidence.

01

Write down the configured engineering range

The lower range value is 0 and the upper range value is 100 % open. The engineering span is the difference between those values; it is not automatically zero-based.

Do this in the product

Open the registered Control-valve position transmitter case so the grader—not the browser copy—owns the expected result.

Open the exercise
02

Convert current into percent of span

Subtract the 4 mA live zero from 18.4 mA, then divide by the 16 mA measurement span. Keep enough precision until the engineering conversion is complete.

Do this in the product

Calculate the fraction separately before typing the final engineering value into the lab.

Open the exercise
03

Apply the engineering span and lower value

Multiply percent span by the configured engineering span, then add 0 % open. The registered expected result is 90 % open within ±0.1%.

Do this in the product

Submit the value and inspect the range, live-zero and tolerance checks returned by the server.

Open the exercise
04

Record the evidence before changing configuration

A calculation mismatch can come from signal measurement, transmitter configuration, PLC card range, program scaling or unit conversion. Preserve the measured current, range, result and timestamp before changing any layer.

Do this in the product

Create an account to retain the attempt, then use a paid workspace to compare cases, keep full history and assign the exercise.

Open the exercise

Core concepts

Know what the evidence means.

The simulator creates a repeatable result; these concepts make that result transferable to real vendor software and supervised practical work.

Live zero

Four milliamps represents the lower engineering value, leaving near-zero current available as fault evidence.

Engineering span

For this Control-valve position transmitter, the span is 100 % open.

Acceptance evidence

The case records the input, expected value, units and ±0.1% acceptance statement instead of returning an unexplained number.

Common mistakes to avoid

  • × Treating command and feedback as the same signal can conceal stiction or a failed linkage.
  • × Adjusting the transmitter before recording the as-found value and configuration.
  • × Using a value with the right number but the wrong engineering unit.
  • × Assuming the PLC input card and transmitter use the same configured range.

Continue in the workspace

Turn this tutorial into retained training evidence.

Run the foundation exercise publicly, then use a subscription for advanced challenges, saved configurations, full attempt history, sharing, assigned paths and team reporting.

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Related learning surfaces

Instrumentation simulator 4–20 mA calibration tutorial Instrumentation training path
Technical reference questions

Questions before you continue.

The fixed 18.4 mA test signal maps to 90 % open on the configured 0 to 100 % open range.